1916-06-01 10.2307/j50000776 6 145 10.2307/j50000776 139 1916 10.2307/40691944 publastrsocipaci 139-145 REVIEWTwo Books on Meteorites. Students of meteorites will be interested in two volumes by Dr. Farrington, Curator of Geology in the Field Museum of Natural History, Chicago, which have appeared recently.A Catalogue of the Meteorites of North America was issued a few months ago as Volume XIII, Memoirs of the NationalAcademy of Sciences; 513 quarto pages of text, and 36 full- page sectional maps of North America. It treats of 247objects or "falls" recognized by Dr. Farrington as bona-nde meteorites up to January 1, 1909. Of the 247, the iron meteorites number 161, the iron-stone meteorites 10, and the stony meteorites 76. Of the three kinds, 3 iron, 1 iron-stone, and 56 stone meteorites were actually seen to fall, but Dr. Farrington is convinced that the remaining 187 "finds" repre- sent real "falls." Doubtful cases have been excluded. The phenomena of each fall and find, the shape, size, chemical composition, and mineralogical structure of each object, are described in good fullness, but completeness is obviously im- possible in the cases which include many specimens in one fall or find. The Canyon Diablo group, for example, includes thousands of meteorites of a great variety of forms and sizes, ocr-38 p-38 140 PUBLICATIONS OF THE and the author necessarily limited the text to such physical and chemical descriptions of selected specimens ás would set forth the characteristics of the great group. Following the data for each meteorite is its bibliography; the author has aimed to give the reference for every paper which makes an appreciable contribution to the subject, but unessential papers are not listed. This volume represents an enormous amount of labor in collecting, reading, compiling, abstracting, editing. Good judgment was demanded constantly. The work appears to have been done thoroly and intelligently. Dr. Farrington makes interesting comments upon the dis- tribution of the 247 meteorites : Considering the province of North America as a "whole, the distribu- tion of known meteorites is most abundant in the eastern United States and in Mexico. Few meteorites are known in British North America and the western United States. There can be little doubt that the apparent scarcity in the localities indicated is largely due to lack of observers, as the writer has elsewhere urged. It is not safe, however, to ascribe too much to this cause, since areas equally populated show great discrepancies in the number of their meteorites. One of the best illustrations of this is the state of Illinois. This is an area of 56,000 square miles in which there are no known meteorites. The greatest massing of meteorites in the whole province of North America occurs in the region of the· southern Appalachians, where the states of Ken- tucky, Virginia, Tennessee, North Carolina, Georgia, and Alabama adjoin. A circle with a radius of 300 miles drawn about Mount Mitchell, North Carolina, as a center, will include nearly half of the known meteorites of North America. Twenty-five of these, or nearly half of the known falls of the continent, are observed falls, and it would seem possible at first thought that many of the meteorites in this area might have come from a single shower. This would reduce the num- ber, but the writer has made a careful study of the history of each meteorite and its geographical relation to those of similar character without finding any support for such a view. Not only does the area contain a large number of observed falls, but the finds embrace a variety of types larger than any known to be produced by a single shower. * * * As regards population in the area, conditions are only moderately favorable, since the area is not very thickly settled. The climate of the region is moist, the average yearly rainfall being 50-60 inches, so that a relatively rapid disintegration of iron meteorites might be expected. Yet in spite of so many conditions unfavorable to their occurrence in large numbers, meteorites are superabundant in this area. This seems to leave little doubt that some force tends to bring about their concentration here. It is noteworthy that this region includes the ocr-39 p-39 ASTRONOMICAL SOCIETY OF THE PACIFIC. 141 highest summits of the Appalachians, and this suggests either the presence of an extra-gravitational force or that a purely obstructive effect has been exerted by the high peaks. Studies of the gravitational effects of mountain masses indicate no force seemingly sufficient to affect the fall of a meteorite, though some such force may exist. Mag- netic influences may also be suggested. Next to the massing of meteor- ites about the southern Appalachians, the most striking grouping seems to be within the borders of Kansas. Within the area of this State, about 82,000 square miles, 15 meteorites occur. Of these, four are observed falls. Those of the western part of the State are all stones, and an effort has been made to show that they may have been the re- sult of a single shower, but the history and characters of the meteorites, to the writer's mind, negative this view. The soil of the western part of Kansas is especially favorable to the finding of meteorites, as it con- tains few terrestrial rocks, but this advantage is perhaps neutralized by the scantiness of the population. The climate is dry, thus tending to the preservation of meteorites. The region is not itself mountainous, but is elevated and within a few hundred miles of the mountain masses which culminate in Pike's Peak. * * * The three greatest meteorite showers of North America have all occurred within the state of Iowa, two of them within 65 miles of each other, the third 130 miles distant from either. * * * It is evident that the distribution of the localities from which meteorites are known, or what may be in short known' as the distribu- tion of meteorites, will be affected by at least four terrestrial factors : (1) density of population, (2) character of population, (3) climate, and (4) character of soil. Density of population will increase the number of meteorites known from a region, because the greater the population the greater the number of observers and the more numerous the chances both that the meteorite will be observed when it falls and that it will be found after it has fallen. As regards character of population, a high order of intelligence is favorable not only to the observation but to the preservation of meteorites. The writer has elsewhere called attention to the fact that the distribution of meteorites on a map of the world is almost exactly that of the Caucasian race. This seems to prove quite conclusively that the distribution of meteorites is largely dependent on the degree of civilization attained in a region. That this factor is more important than density of population is shown by the fact that no meteorites are known from China in spite of its immense numbers of people. In the province of North America it is hardly likely that the different degrees of intelligence existing in 'different regions would exert any discernible influence on the number of meteorites known. As regards climate, aridity may be doubtless considered favorable and humidity unfavorable to the preservation of meteorites. In a humid climate the iron meteorites disintegrate much more rapidly than in an arid climate, and to a certain extent the same is true of stone meteorites. As regards character of soil, it is obvious that soils free of rocks ocr-40 p-40 142 PUBLICATIONS OF THE would be most favorable to the finding of meteorites. The existence of such soils in Kansas and Texas has led to the discovery in those regions of meteorites that would probably have been overlooked in stony localities. An iron meteorite is, of course, more likely to attract attention in any soil than a stony meteorite, but the latter is quite likely to be overlooked in stony soils. From the above it appears that the most favorable terrestrial conditions for the finding of meteorites are those of a dense, intelligent population living in an arid climate and upon a pebbleless soil. Such conditions are not likely to exist together, but now one and now another will predominate in any given region. To a certain degree the absence of one is likely to offset the presence of another, but where several of these conditions are lacking and a preponderance of meteorites occurs other reasons must be sought. The eastern states of the United States as compared with the western states possess a relative dense population, but a moist climate and rocky soil. Canada has a scanty population, a moist climate, and rocky soil. Mexico has the advantage of an arid climate but the disadvantage of a scanty and illiterate population, and a more or less rocky soil. The second volume by Farrington is on Meteorites: Their Structure, Composition and Terrestrial Relations; octavo, pp. 233 -f χ and one chart.* It is in the nature of a general treatise on the subject, prepared from the viewpoint of the mineralogist rather than of the astronomer. The reviewer acknowledges the inadequacy of what he is writing concerning the book on that account. However, the book has many points of contact with astronomical problems, and is of interest to all students of nature. The author describes three classes of meteorites - stone, iron-stone, and iron meteorites, which pass from one class to the next by almost insensible gradations - and explains how specimens usually may be distinguished as real meteorites or as of terrestrial origin. "No single criterion can be given for distinguishing meteorites from masses of terrestrial origin. Only by combining several features can the positive determina- tion of a meteorite be made." Even so, it seems, there must be cases in which the meteoric origin cannot be ascertained with certainty, "So far as the iron meteorites are concerned, the presence of nickel is essential. No iron meteorites are known without nickel. Yet this alone does not prove meteoric origin, since terrestrial nickel-irons are known. Terrestrial nickel-irons, however, have a percentage of nickel either * Published by the author. ocr-41 p-41 ASTRONOMICAL SOCIETY OF THE PACIFIC. 143 lower (3%) or higher (35%) than that of meteorites, so that a percentage of nickel between 8% and 20% is a pretty sure indication of meteoric origin/' Other lines of evidence have somewhat similar values, and must be treated with circumspection. We quote a few specially interesting facts from the book : Of about 700 meteroites now recognized, only about one-half were actually seen to fall. * * * Of about 350 observed falls only 10 have been of iron meteorites. On the other hand, among meteorite "finds," the iron meteorites largely predominate. This is chiefly for the reason, doubtless, that the iron meteorites * * * attract the attention of the ordinary observer much more quickly than the stone meteorites. The latter show to the casual observer no striking differences from the terrestrial rocks, and arethus usually overlooked. No meteorite fall has ever been positively known to have been destructive of human life. * * * Perhaps the most narrow escape which has ever been experienced was that of three children in Braunau at the time of fall of that meteorite in 1847. This meteorite, an iron weighing nearly 40 pounds, fell in a room where these children were sleeping and covered them with debris, but they suffered no injury. About 20 of the most interesting observed falls of meteor- ites are described at some length. The part played by our atmosphere in resisting the passage of meteorites is discussed, in somewhat general terms, to about the extent that the reader of popular astronomical articles will desire, but not to meet the needs of the student of the subject. The times of fall, with reference to years, months of the year, and hours of the day, are discussed, but unfortunately the value of the discussion is reduced by the great number of errors in the summations (page 41), as well as by weak- ness in the astronomical aspects of the problems. We quote from p. 44: "All meteorites which move in orbits which are parabolic about the Sun have a velocity of 26.16 miles per second/' This sentence could easily puzzle many readers, but one who already understands the subject can interpret the author's idea. It seems to mean that a meteoric body travel- ing around the Sun in a parabolic orbit which intersects the Earth's orbit will at the point of intersection have an orbital velocity of 26.16 miles per second; and, therefore, a "para- bolic" meteorite (a body that comes down thru our atmos- ocr-42 p-42 144 PUBLICATIONS OF THE phere) possesses intrinsically that velocity. One ought to recall that as the Earth's distance from the Sun varies by as much as three million miles in the course of a year, so the parabolic velocity of a meteorite will vary correspondingly. And should the reader be left with the thought that the orbits of meteoritic bodies are parabolic in general? The work of H. A. Newton and of W. H. Pickering is counter to the idea. The author refers to the opinions of these investigators, but much later in the book," on page 213. The author's description of meteoritic showers records many interesting facts. "In each of the showers of Pultusk and Mocs more than 100,000 stones fell. In the shower of Hol- brook, 14,000 stones fell, and in that of V Aigle 2-3,000." "All observed showers have been of stones, but the finding of numerous individuals of iron in single localities such as Toluca and Canyon Diablo indicates that showers of meteoric irons sometimes take place also." "The largest individual meteorite known is one of the Cape York, Greenland group," an iron meteorite weighing 36^4 tons, brought home by the Arctic explorer Peary and de- posited in The American Museum of Natural History, New York City. Chapters of the book are devoted to Forms of Meteorites, Crusts of Meteorites, Veins of Meteorites, Structure of Meteorites, Composition of Meteorites, Origin of Meteorites, Terrestrial Rotations and Meteorite Collections. Twenty-nine chemical elements have been found in meteor- ites in quantities sufficient for accurate study. The author reviews the conventional ideas of the origin of meteorites, but wisely comes to no definite conclusion. The great collections of meteorites in Europe and America are located and. each given a sentence or two of description. The principal collections in the United States are at Yale University, Harvard University, Amherst College, the Ameri- can Museum in New York, the National Museum in Wash- ington, and the Field Museum in Chicago. The author states that the Chicago collection is "now the largest in the world. This collection was inaugurated in 1894 at the time of the founding òf the Field Museum by purchase of collections ocr-43 p-43 ASTRONOMICAL SOCIETY OF THE PACIFIC. 145 from George F. Kunz and Ward's Establishment. In 1912 the private collection of Professor Henry A. Ward, number- ing over 600 falls (and finds), was added to the collection, and thus the most representative series of meteorites in the world was secured." The growth of American collections has been remarkable. It is hoped that they will be made the sub- jects of fruitful study, with a view of contributing their share in solving the many problems of meteors and meteorites still before us.W. W. Campbexl. ocr-44 p-44 eng 164 June, 1916 Publications of the Astronomical Society of the Pacific 28 Campbell W. W. 1 10.2307/i40030372 book-review 00046280 Farrington Farrington